This invention generally relates to rotary antenna positioning systems and more specifically is directed to a microprocessor controlled automatic antenna positioning system in which transmitter location and received signal strength are used in optimally positioning the antenna.
Rotary antenna positioning systems are used in various communications systems, most popularly in conventional television and radio receivers. These systems may be either manual and under the direct control of the user, or viewer, or they may be automatic in the sense that the antenna is positioned automatically in response to the station, or channel, selected. Automatic antenna positioning is desirable since the untrained user generally finds it difficult to optimally position the antenna for receiving the strongest signal. Transmitting antenna sidelobe radiation, the presence of widely located stations transmitting the same channel, or frequency, and various other factors beyond the viewer's control frequently make accurate manual antenna positioning difficult, if not impossible.
The performance of automatic antenna positioning systems is frequently degraded by electric motor interference with the reception and detection of the incoming signal. In addition, in conventional rotary antenna positioning systems the antenna drive system is coupled to the channel selector and tuning systems by means of a large number of electromechanical relays and switches which not only are electrically noisy, but also generally have low reliability.
From the discussion of the aforementioned problems, it can be seen that the orientation of the receiving antenna is a critical factor in optimizing the reception of the transmitted signals. These problems may be compounded by the use of receiving antennas having inceased directivity for bringing the weaker signals. Antenna positioning is critical not only in urban areas because of the presence of reflected signals from large buildings, but also in rural areas where several sources of a transmitted signal may be available at a particular location.
The prior art discloses many approaches in positioning a rotary antenna. One such approach is described in U.S. Pat. No. 4,263,539 to Barton wherein a signal representing the actual position of the receive antenna is generated and compared with a signal representing the desired position with both signals provided to a comparator, the output of which is a direction control signal. This system is primarily analog in nature with the desired position signal source for generating a signal representing the desired position of the antenna typically being a potentiometer, the resistance of which is responsive to the channel selected. U.S. Pat. No. 3,229,176 to Curll, Jr. et al describes a rotatable shaft positioning system having manual and automatic modes wherein the angular displacement of the channel selector is converted to corresponding rotary antenna drive signals. Thus, antenna rotation is correlated with channel selector knob rotation. U.S. Pat. No. 3,200,314 to Iroler also discloses a rotary antenna positioning system which is directly coupled to the channel tuner shaft that each position of the tuner shaft corresponding to a selected channel electromechanically causes the rotary antenna to be oriented in a corresponding position. Television antenna rotating servo systems are described in U.S. Pat. Nos. 2,794,162 to Lifsey and 3,248,730 to Neumeyer.
Refinements in the prior art in the general approach taken to optimally position a rotary antenna have been numerous, as evidenced by the aforementioned systems. Typical of these improvements are systems in which multiple antenna rotations in searching for a selected station is avoided and wherein the antenna is moved directly to the desired orientation with the smallest displacement angle therebetween subtended. Examples of systems embodying these improvements can be found in U.S. Pat. Nos. 2,989,680 to Weiser et al; 3,448,360 to Pohl; and 3,826,964 to Byrne. These approaches generally represent improvements over earlier antenna positioning systems, but fail to provide a system capable of accurately positioning the receiving antenna with respect to several signal sources and where several operating parameters are utilized for more accurately positioning the receiving antenna relative to the transmitted signal source.